1. Field of the Invention
The present invention relates to an optoelectronic conversion header applied to a high-speed LSI package and a manufacturing method of the optoelectronic conversion header, an LSI package with an interface module equipped with the optoelectronic conversion header, and an optical interconnection system.
2. Description of the Related Art
Recently, a performance of large-scale integrated circuits (LSIs) is significantly improved to achieve a high speed processing due to an improved performance of electronic devices such as bipolar transistors and field effect transistors. However, even though the processing speed is improved in the LSI, a printed wiring board mounting the LSI is not so sufficiently improved as to have a sufficiently high signal transfer rate or speed for transferring a signal from the high speed processing LSI. The transmission speed in the printed wiring board is restricted due to following reasons. In the printed circuit board, it is necessary to prevent a reduction in a signal quality resulting from an increase in a transmission loss, noise and electromagnetic interference in electric wires due to an increased operation frequency. The longer lines in the circuit board need more restraint on the operation frequency to ensure the satisfactory signal quality. In this background, it is recognized in a common sense that a system speed is limited by a packaging technique rather than the LSI operation speed.
In view of such problems in the electrically wired systems, several optical devices have been proposed in which the LSI is connected via optical waveguides. In the optical waveguide, a signal loss has not frequency dependency even in a range between a direct current and 100 GHz or higher, and noise is not produced due to the electromagnetic interference of wiring paths and a variation in a ground potential. The optical waveguide can readily realize a data transmission capability of several tens of Gbps. An application of the optical waveguide is proposed in Nikkei Electronics, No. 810, pp. 121-122, Dec. 3, 2001, in which an interface module is directly mounted on an interposer for interconnecting the LSI to a peripheral device to transmit a high-speed signal between the LSI and the peripheral device.
In order to realize the optical interconnection disclosed in Nikkei Electronics, No. 810, pp. 121-122, Dec. 3, 2001, the interposer is essentially provided with an optoelectronic conversion component which converts an optical signal into an electric signal or converts the electric signal into the optical signal, and the optoelectronic conversion component is further required to have a small size in order to be arranged in the interposer. This small optoelectronic conversion component has a structure in which a surface emitting laser is optically coupled to an optical fiber, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-347072. There has been proposed in connection with this structure in Jpn. Pat. Appln. KOKAI Publication No. 2001-281503 which discloses metal projections having different heights or a block having an inclined plane are used to obliquely dispose an optical semiconductor device such as semiconductor lasers to restrain external optical feedback. There has been also proposed in Jpn. Pat. Appln. KOKAI Publication No. 2001-284608 in which a photodiode (PD) of rear surface incidence type is adhesively bonded onto a fiber having an end face obliquely cut with respect to an optical axis.
The conventional structure disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-347072 has a problem that if the optical fiber is inserted in a support member provided with the surface emitting laser to optically couple the surface emitting laser to the optical fiber for assembly of the structure, the optical fiber contacts an active area of the optical semiconductor device and this contact easily damage the optical semiconductor device. There is also a problem that since the surface emitting laser is proximately disposed in parallel with the optical fiber, the external feedback light rays are input to the surface emitting laser and easily generate so-called external optical feedback noise.
A conventional structure for suppressing the external optical feedback noise has been disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-281503. However, there is a problem in which a temperature change easily varies an inclination angle of the optical semiconductor device in this structure that is provide with the metal projections having different heights or the block having the inclined plane to obliquely dispose the optical semiconductor device. In this structure, if thermal expansion is caused in the metal projections or the block, various changes in heights of the metal projections or the block are produced and the inclination of the optical semiconductor device is changed. In the conventional structure disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-281503, the external optical feedback noise is also generated depending on temperature, so that the excessively large inclination angle is set to avoid the external optical feedback noise. Another problem is the excessively low optical coupling efficiency between the surface emitting laser and the optical fiber resulting from the excessive setting of the inclination angle of the optical semiconductor device. Moreover, the conventional structure in Jpn. Pat. Appln. KOKAI Publication No. 2001-281503 is complicated in the structure, and not suitable for mass production.
Furthermore, in the conventional structure disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-281503, the entire optical semiconductor device is inclined with respect to the member supporting the optical fiber. The conventional structure has a gap between an end face of the optical fiber and the optical semiconductor device, which has a distance delivered from a multiplication of the inclination angle and a length between an optical semiconductor device end and the active area. Thus, a photo detection area needs to be a small diameter. Especially in a combination of the high-speed photo detector, light rays exiting from the optical fiber are diverged to the high-speed photo detector, leading to a problem that the optical coupling efficiency is easily decreased. The external feedback light rays does not regarded as noise between the photo detector and the optical fiber. However, in such a case as in the inter-LSI wire lying over a relatively short distance of about 1 m at the maximum, most of the external feedback light rays are generated due to a reflection on the optical fiber end face on a photo detector side or a reflection on a photo detector surface and the reflection light rays return to a light emitter via the optical fiber so that the external optical feedback noise is induced. Therefore, measures for prevention of the light reflection are also needed on the photo detector side, and the photo detector needs to be inclined in the conventional structure of Jpn. Pat. Appln. KOKAI Publication No. 2001-281503, resulting in the problem that the optical coupling efficiency is decreased.
Another method to incline the optical semiconductor device is, as in Jpn. Pat. Appln. KOKAI Publication No. 2001-284608, to obliquely form the optical fiber end face together with a ferrule and adhesively bond the optical semiconductor device to this end face. However, this method requires a polishing process to form the end face of the optical fiber into the inclined surface so that it is substantially difficult to significantly reduce costs. In an application of the interconnection between the LSI and the peripheral devices, a permissible cost is low as compared with costs in optical communications or LANs, and there is a problem that a time-consuming process such as the polishing process cannot be permitted.